The invention relates to a mounting for an optical assembly, and to methods of mounting an optical assembly to an object.
The essential elements of a camera are a lens system to focus light on to an image plane, together with a sensor located at that image plane. Initially, this xe2x80x9csensorxe2x80x9d was photoresponsive film. For many applications it is now desirable to have a sensor which has electrical signals as an output (such as charge coupled detectors (CCD)). It is particularly desirable for this sensor to have a digital output, as it is particularly easy to transfer digital data from one device or application to another, and digital data can be stored and transferred with high fidelity.
The versatility of use possible with digital sensors has been restricted, because conventional digital sensors have been relatively expensive. However, improvements in technology have now reduced the cost of such sensors. A particularly advantageous sensor type is the CMOS sensor, of which an example is described in EETimes, Oct. 12, 1998, Issue 1030. Sensors of this type can be produced to be particularly inexpensive. The existence of cheap digital optical sensors opens up new possibilities for sensor application.
The basic design of a camera system using a CMOS sensor is shown in FIG. 1. The details shown would be substantially similar if another sensor type were chosen. The elements of this camera system will now be described.
The sensor 16, mounted on a PCB substrate 18, is electrically connected to the substrate by connectors 17. The camera system may be in communication, or adapted to communicate, with other system elements through electrical connection to PCB substrate 18. The sensor 16 and substrate 18 are mounted in a sensor housing 15 (in alternative designs the PCB substrate 18 may be larger and not xe2x80x9cwithinxe2x80x9d a sensor housing in this wayxe2x80x94provided that means are provided to ensure that unwanted light does not reach the sensor). The sensor housing 15 is engaged with lens housing 4xe2x80x94in the arrangement shown, this engagement is adjustable (with screw thread 10) to allow for focussing. Typically, the engagement will be either fixed on assembly (possibly after a focus adjustment step during assembly), but play may be allowed for limited user adjustment depending on design.
The lens housing 4 holds a first lens 1 (typically the main objective lens), which here is held in the housing by retaining ring 19. Both housings 15, 4 and the retaining ring 19 can be conveniently produced as plastics mouldings. Additional optical elements 3 required for satisfactory imaging onto the sensor 16 are mounted within the housing. Depending on the imaging required, there may be none, one or more discrete optical elements used for this purpose in addition to the objective lens 1. Typically, such a system will also need an aperture stop 2 to limit the amount of light entering the system. Such stops are generally thin sheets of metal, coloured black. Here, both stop 2 and additional optical elements 3 are fixed within lens housing 4, but in alternative arrangements one or both of these may be adjustablexe2x80x94normally, however, only adjustment of size of the stop 2 is required, rather than adjustment of its position.
The camera is mounted to a further object 6 by a combination of the retaining ring 19 and a nut 5. While this arrangement is generally effective, it may not be ideal for particular applications. For example, if the camera is mounted to be an internal part of some larger object, it may be difficult for the screw thread to be tightened effectively. The possibility of the nut 5 working itself loose may also be particularly undesirable where a very tight seal is requiredxe2x80x94such as where the connection point 6 to the further object is a flexible material (e.g. the fabric material of a child""s toy). It is desirable to achieve a reliably secure fixing of the optical assembly, but without any risk of damage to the delicate optical assembly itself, and preferably at low cost and suited to the mounting of cameras in relatively inaccessible locations.
Accordingly, in a first aspect the invention provides a method for mounting an optical assembly in an aperture of a body, the body having a first face and a second face between which the aperture extends, the method comprising: placing the optical assembly within the aperture such that a flange of the optical assembly abuts the first face of the body around the aperture; and deforming a deformable element disposed around the optical assembly such that the deformation of the deformable element causes a fixed engagement to be made between the optical assembly and the second face of the body around the aperture.
The invention therefore allows an effective, but extremely simple and versatile, mounting of an optical assembly to a body. The optical assembly is fixed in position relative to the body, and the disposition of the deformable element post-deformation is such as to render the mounting secure.
The deformable element may be deformable by pressure or by heat or both. A heat-deformable element may also be a glue (in the sense that it forms a chemical bond with at least one of the system components that it abuts)xe2x80x94if the body is a fabric or other flexible (or even elastic) material, then it may be particularly useful for the deformable element to bond with the bodyxe2x80x94but it may simply be adapted to reflow and cool into a mechanically rigid form which provides a physical barrier to breaking of the fixed engagement between the optical assembly and the body.
If further elements are provided for association with the optical assembly, it is advantageous to provide a mounting collar as an additional element. This is placed around the optical assembly where it extends from the second face. Deformation of the deformable element provides fixed engagements between the mounting collar and the optical assembly, and between the mounting collar and the second face of the body around the aperturexe2x80x94heating of the mounting collar may be the method used to provide heat to a heat-deformable element (this is particularly effective if the mounting collar is made of a metal or another material with high thermal conductivity). This approach may be used if the optical assembly is to be connected to a camera assemblyxe2x80x94the mounting collar may be provided with a means for connection to the camera assembly, or may even be a part of the camera assembly itself.
In a second aspect, the invention provides an optical assembly kit for use in mounting an optical assembly in an aperture of a body, the body having a first face and a second face between which the aperture extends, the kit comprising: an optical assembly adapted for placement within the aperture such that a flange of the optical assembly abuts the first face of the body around the aperture; and a deformable element adapted for deformation after placement of the optical assembly within the aperture such that the deformation of the deformable element causes a fixed engagement to be made between the optical assembly and the second face of the body around the aperture.
The kit is advantageously adapted to the method as described above. In particular embodiments, the kit comprises a camera assembly, and a mounting collar for mounting the camera assembly to the optical assembly. In this case, it is advantageous that deformation of the deformable element provides fixed engagements between the mounting collar and the optical assembly, and between the mounting collar and the second face of the body around the aperture.